Sun Tunnel vs Skylight Cost Difference Calculator

How this calculator works

This calculator compares typical UK supplied-and-fitted price ranges for the two options, drawn from published 2026 industry cost guides. Your inputs scale those base ranges: the calculator multiplies the per-unit range for each option by the number of units and by adjustment factors for the choices you make below, then shows both totals side by side along with the estimated difference between them. Because real quotes vary, everything is expressed as a range from a realistic low to a realistic high rather than a single figure.

A sun tunnel typically costs around to fitted in 2026 against to for a skylight, making the tunnel the budget route to natural light. The two are not interchangeable, though: a skylight needs the room to sit directly under the roof surface, while a sun tunnel can pipe light through a loft space into rooms a skylight could never reach.

Number of units

Enter how many units you are comparing. Both products are usually fitted one per room.

Specification level

Two windows that look similar from the street can sit at very different price points. Budget products use simpler profiles, standard hardware and basic glass. Mid-range covers the typical A-rated units most UK installers quote by default. Premium covers high-end systems with upgraded security hardware, better thermal performance, special finishes or designer profiles, and typically adds around 30 percent to the price.

Where you live

Labour rates are not uniform across the UK. Published cost guides consistently show installation prices in London and the South East running roughly 20 to 30 percent above the national average, driven by higher labour costs, travel, parking and congestion charges. The calculator applies an uplift of around 20 percent if you select London and the South East. Product prices themselves are broadly similar nationwide, so the difference mostly reflects fitting costs.

What else affects the price

Skylights and roof windows deliver far more light, plus a view and optionally ventilation, and they add more perceived value to a room. Sun tunnels deliver a soft, diffused light with no view and no airflow, but they install in hours with minimal structural work, making them ideal for internal hallways, landings, bathrooms and cupboards. If the room touches the roof and the budget allows, a skylight or roof window is usually the better long-term buy; if the room is landlocked under a loft, the sun tunnel is often the only realistic option.

Planning permission, building regulations and certification

Most roof glazing falls under permitted development rights, provided the units do not project more than 150 millimetres above the roof plane and sit no higher than the highest part of the roof, but conservation areas, listed buildings and flats have tighter rules, so check with your local planning authority before ordering. Building regulations apply regardless of planning status, covering structural alterations, thermal performance, safety glazing and, in loft conversions, escape and ventilation requirements. Installers registered with a competent person scheme can self-certify that replacement glazing complies with the regulations and issue a certificate you will need when selling the property; for structural roof work, building control involvement is normally required.